This project addresses the issue of chemoprevention of gastric cancer by blocking the progression of chronic atrophic gastritis and intestinal metaplasia, a lesion of the gastric mucosa which identifies patients at high risk. It represents the continuation of studies in the population of Narino, Colombia, where a cohort of 1788 subjects has been followed for over 5 years. 380 patients with chronic atrophic gastritis and 740 with intestinal metaplasia of the gastric mucosa will be entered into a randomized double blind clinical trial testing the role of antioxidants (ascorbic acid and beta-carotene) as well as anti-Helicobacter pylori therapy (bismuth sub-salicylate and furazolidone). 14C urea breath test will be used to monitor H.p. relapses. A factorial design will be utilized. The effects of the agents will be evaluated with the following intermediate end-points: histology of cancer precursors (small intestinal metaplasia, colonic metaplasia and dysplasia), mucin histochemistry, nucleolar organizer regions (AgNO3-NORs) and morphology of replication zone evaluated with PCN-cyclin monoclonal antibodies. Progression and regression rates for each parameter will be compared between intervention and placebo groups.